APPLICATIONS OF GIS FOR HIGHWAY SAFETY
Peer Exchange Summary Report
September 14-15, 2011
- Prepared for:
- Office of Planning
- Federal Highway Administration
- U.S. Department of Transportation
- Prepared by:
- Policy, Planning, and Organizational Analysis Center of Innovation
- John A. Volpe National Transportation Systems Center
- Research and Innovative Technology Administration
- U.S. Department of Transportation
III. PRESENTATIONS AND DISCUSSION
Jennifer Inzana and Rick Conard
Although Massachusetts is a small state in size, it experiences a significant volume of vehicle crashes. In 2009, for example, more than 117,700 crashes were reported. The Registry of Motor Vehicles (RMV) is the legal custodian of crash data for the state. It receives crash reports from police and operators, and then enters or imports crash data into the state’s Crash Data System (CDS).
MassDOT, which maintains the Road Inventory GIS file in its Planning office, is a major user of the RMV’s crash data. Specifically, MassDOT’s Traffic Engineering Office focuses on crash location data and crash characteristics for all roads in the state, the preparation of high crash location reports, and the matching of crash data with the roadway inventory file using GIS tools (MassDOT has ability to edit crash location data in RMV files). Unfortunately, MassDOT has found that most police agencies do not supply crash location coordinates, and those that do, do not often use a consistent, reliable coordinate referencing system.
Screenshot of MassDOT’s interactive crash mapping tool.
For this reason, and because MassDOT needed a way to geocode crash locations, MassDOT hired a consultant to develop a crash geocoding application that could connect to crash data and GIS databases for the state. In use since May 2006 and continually refined since, the crash geocoding application automatically attempts to locate all of the new or changed crash records from the RMV crashes each day. The layers used for the crash geocoding include:
- Road inventory/routes
- Mile markers
- Town boundaries
- Navteq roads
The crash locations are georeferenced using information on:
- Intersection and distance from intersection
- Street address number
- Route and mile marker
- Route and exit number
- Learned intersections
Approximately, 84 percent of crashes in 2009 were automatically geocoded. MassDOT staff does have the ability to inspect and/or geocode crash data manually. The application has an interactive screen with a GIS map that allows the user to view and edit the data most relevant to the reported crash location. The user also has the ability to inspect the collision diagram(s) and crash narrative(s), assuming the crash report(s) was submitted electronically. Any location edits and new X, Y coordinates made are “pushed back” to the RMV data file each night. Any edits made to the master record do not alter the original data that the police submitted. The manual approach, however, is labor-intensive and time-consuming.
In any case, MassDOT uses the crash data to analyze the state’s top crash locations, including top pedestrian/vehicle and bicycle/vehicle crash locations. The “top crash” designation is based on crash frequencies and severities, not crash rates. Results of MassDOT’s analyses are used as inputs into a statewide “Top 200” at-grade intersections report2 (latest listing using 2007-2009 data was released in August 2011) and to report on the top five percent of all crash location clusters for the HSIP.
In the future, MassDOT anticipates releasing a web-based version of its internal crash portal that would allow the public to query and view crash data. MassDOT also hopes to continue to improve the accuracy of roadway names in both the road inventory file and in the RMV’s CDS.
MassDOT described some of the challenges it faces in analyzing crash data. They include:
- Excess location data (leading to conflicting locations)
- Lack of location data
- Location data entered into incorrect location boxes on form by police office
- Mismatch or incorrect street names between Road Inventory and crash reports…
- Lack of crash report submittal or underreporting by police department
- Lack of data entry of operator reports by RMV
- Outdated information in RMV data entry road name drop-down “pick lists” …
- Delay by RMV to officially close a crash file for any given year
- Difficulty quantifying number of crashes at interchanges and rotar
- Not data owners, therefore cannot…change roadway file or crash data entry process.
Comments, Questions, and Answers
How many law enforcement agencies are providing information that goes into the top crash locations report?
There are approximately 300 police agencies providing crash information. This includes state police, Massachusetts Bay Transportation Authority (MBTA) police, and campus police. Not all MA towns have law enforcement agencies.
Are all field reports captured on paper?
About two thirds of the reports are still submitted as paper reports. Many local police agencies collect or enter data into their own computerized records management systems, but do not submit their data electronically to the RMV. Instead, their reports are printed and sent to the Registry of Motor Vehicles (RMV) to get keyed in again. The RMV enters the information from the paper reports into a computerized “master record.” MassDOT has been an advocate for electronic submission of crash data so that police are able to enter these data directly into the statewide crash data system file. MassDOT is also considering the feasibility of a scanning solution for all crash reports, which would enable MassDOT to more easily view and archive the images of all paper crash reports.
Does MassDOT have a way to audit or check the validity of the locations indicated in crash reports?
MassDOT does not systematically check the validity of locations. If any potential problems are noticed when the data are being entered in the master record, then staff will examine the location more closely. Police will often use the most convenient landmark (e.g., the nearest exit) to indicate a crash’s location, when that landmark may not be the true crash location. MassDOT often receives crash data rounded off to the nearest mile, which could result in location errors off by an entire town especially since all of the land area in MA is incorporated into cities and towns. On the other hand, MassDOT can locate all crashes to a city or town, which is at a more fine grained level than perhaps is possible in rural states.
What is meant by “collision diagrams?”
At MassDOT, collision diagrams refer to the drawings that law enforcement officers make in the crash report. MassDOT manually compiles/draws composite crash diagrams from original crash reports for locations that are being more intensively studied to analyze safety issues.
How much of the crash report data is available to engineering staff?
Anyone internally at MassDOT can access the data through a web-based program. When consultants involved in a project request crash data, MassDOT provides them with an Excel file that includes information on all of the crashes in a town or area within a year. The consultants will use the spreadsheet to find the data they seek.
How is the crash report data being used in-house?
MassDOT uses the data for road safety audits. All HSIP projects done now are done through a data-driven process. Project proponents must show that safety is a concern.
However, evaluation has sometimes been problematic due to data quality issues and the time lag associated with when the crash data becomes available. MassDOT currently does not have a micro-forming or electronic imaging process for the paper reports received. Any before-and-after analyses performed require the safety specialist to have the crash report and its narrative in hand. MassDOT has a paper retention deadline after which the crash report is destroyed, causing some data to be eventually lost. Additionally, police departments do not collect and report crash data uniformly. This challenge can be compounded in towns that habitually do not provide crash reports at all, especially when someone tries to evaluate a transportation improvement in those towns.
Is there a standard form for police department to enter crash data?
Yes. MA has a standard paper form. However, there is no standard for the electronic records management systems used by local police agencies. Towns often want to maintain their autonomy, leading to a number of vendors serving various police departments across the state. MassDOT is not able to dictate or enforce what the various systems do and/or how they validate data. While MassDOT would like to have crash data at the source, the lack of data standards can cause issues for attributes as fundamental as latitude and longitude. Some towns use decimal degrees, others use degrees, minutes and seconds, while others use state plane meters.
What are some of the challenges in releasing the crash viewer system externally?
The primary challenge is a bureaucratic one; IT staffs have some security concerns. Hopefully, in the near future the system will be made available externally.
Does MassDOT give a confidence scoring when crash locations are geocoded?
Yes. Crashes that MassDOT manually locates are given a confidence of 100%. Other scenarios result in different confidence levels. Any crash location with a score of lower than 90% is considered “low confidence.” The low confidence locations get geocoded but are then sent into the queue for a person to review and validate.
How often does MassDOT produce crash maps or pin maps? Is the annual report the primary output?
The annual reports are the primary focus. Few maps are produced. The team does develop a crash clusters map that is available externally without the crash data behind it. When MassDOT does distribute crash data, it is in a flat Excel file and has X and Y coordinates included, thus providing the public the materials to produce maps should it have the desire and necessary GIS to do so.
 Items noted in red are editorial changes due to Dr. Jeffrey Everson, former I-93/I-95 Interchange Task Force Member, 2004 – 2007.